serial: imx: use locking to stop concurrent access of UCR1

Several places are accessing the UCR1 register without locking.
This probably will cause a race issue when another thread
is accessing the same register.
Add locking to preventing concurrent access of the UCR1 register.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index eb2210f..c851247 100644 (file)
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -731,6 +731,9 @@ static int start_rx_dma(struct imx_port *sport);
 static void imx_dma_rxint(struct imx_port *sport)
 {
        unsigned long temp;
+       unsigned long flags;
+
+       spin_lock_irqsave(&sport->port.lock, flags);
 
        temp = readl(sport->port.membase + USR2);
        if ((temp & USR2_RDR) && !sport->dma_is_rxing) {
@@ -744,6 +747,8 @@ static void imx_dma_rxint(struct imx_port *sport)
                /* tell the DMA to receive the data. */
                start_rx_dma(sport);
        }
+
+       spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
 static irqreturn_t imx_int(int irq, void *dev_id)
@@ -873,6 +878,9 @@ static int imx_setup_ufcr(struct imx_port *sport, unsigned int mode)
 static void imx_rx_dma_done(struct imx_port *sport)
 {
        unsigned long temp;
+       unsigned long flags;
+
+       spin_lock_irqsave(&sport->port.lock, flags);
 
        /* Enable this interrupt when the RXFIFO is empty. */
        temp = readl(sport->port.membase + UCR1);
@@ -884,6 +892,8 @@ static void imx_rx_dma_done(struct imx_port *sport)
        /* Is the shutdown waiting for us? */
        if (waitqueue_active(&sport->dma_wait))
                wake_up(&sport->dma_wait);
+
+       spin_unlock_irqrestore(&sport->port.lock, flags);
 }
 
 /*
@@ -1194,9 +1204,11 @@ static void imx_shutdown(struct uart_port *port)
                        dmaengine_terminate_all(sport->dma_chan_tx);
                        dmaengine_terminate_all(sport->dma_chan_rx);
                }
+               spin_lock_irqsave(&sport->port.lock, flags);
                imx_stop_tx(port);
                imx_stop_rx(port);
                imx_disable_dma(sport);
+               spin_unlock_irqrestore(&sport->port.lock, flags);
                imx_uart_dma_exit(sport);
        }